Self-distracting cage

ABSTRACT

Various spinal implants and methods for stabilizing the spine are provided. In one exemplary embodiment, a spinal implant is provided having an expandable container with an interior volume that is selectively expandable between a compressed condition and an expanded condition. The expandable container is coupled to a superior endplate member having a bone-contacting surface and an engagement surface effective to mate with a superior surface of the expandable container, and an inferior endplate member having a bone-contacting surface and an engagement surface effective to mate with an inferior surface of the expandable container. In addition, at least one inlet port is formed in the expandable container and is effective to communicate a fluid to at least one cavity disposed within the interior volume of the expandable container.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/792,871, filed Jul. 7, 2015. U.S. application Ser. No. 14/792,871 isa continuation of U.S. application Ser. No. 13/561,271, filed Jul. 30,2012, and now issued as U.S. Pat. No. 9,101,486. U.S. application Ser.No. 13/561,271 is a divisional of U.S. application Ser. No. 11/750,113,filed May 17, 2007, and now issued as U.S. Pat. No. 8,273,124. Thecontents of each of these applications are incorporated herein byreference in their entirety.

FIELD

The present invention relates to methods and devices for spinalstabilization and fusion, and particularly to an expandableintervertebral implant.

BACKGROUND

A leading cause of lower back pain arises from lumbar intervertebraldisc pathology caused by degeneration of the intervertebral disc. As adisc degenerates, the nucleus and annulus functions are compromised. Thenucleus becomes thinner and unable to handle compression loads. Theannulus fibers become redundant as the nucleus shrinks. The redundantannular fibers are less effective in controlling vertebral motion. Thedisc pathology can result in the bulging of the annulus into the spinalcord or nerves, narrowing of the space between the vertebra where thenerves exit, tears of the annulus under abnormal loads caused byexcessive motion between the vertebra, and disc herniation.Additionally, lower back pain may be caused by collapse of the disc andthe dysarthrosis of an unstable or degenerative vertebral facet joint. Atechnique for managing these problems is to remove the problematic discand replace it with a porous intervertebral fusion device that restoresdisc height and allows for bone growth therethrough for the fusion ofthe adjacent vertebra.

In general, delivery of conventional intervertebral fusion devicesrequires significantly invasive implantation procedures. In someconfigurations, the intervertebral implants are not adjustable by thesurgeon during an open surgical procedure. Therefore, the surgeon mustchoose the size that most closely matches the desired height, length,and width dimensions, and then make the implant fit. Because theseimplants are of a predetermined size and shape, the implant site mustcorrespond to the implant configuration. This can require extensive sitepreparation to complete implantation. Fusion devices with parallelsuperior and inferior surfaces either fit tightly posteriorly andloosely anteriorly, or require removal of vertebral bone in order to fitposteriorly. Extensive site preparation such as this can compromise thesuccess of the implantation procedure by causing excessive damage to thereceiving vertebral elements. In addition, open surgical implantation ofposterior implants requires excision of stabilizing muscles, ligaments,tendons, and bony structures such as facet joints. The implants musttherefore overcome the destabilization caused by the surgery, as well asprovide additional stabilization to promote bony fusion. In addition,open anterior surgery in the lumbar spine can present risks due to theclose proximity of the aorta and bifurcation of the aorta.

To combat some problems associated with open anterior surgeries,minimally invasive procedures have been developed. Current implants, orinner body cages, used in minimally invasive procedures, however, arestill unable to conform to the necessary lordotic angle between adjacentvertebra. In addition, surgeons must rely on high manual forces todistract (dilate) the disc space. Finally, current cages do not have ashape that is optimal in terms of support.

Accordingly, there is a need for instrumentation and techniques thatallow for a self-distracting, self-leveling, and adjustable inner bodycage that can be easily inserted and positioned.

SUMMARY

The present invention provides various spinal implants and methods forstabilizing the spine. In one exemplary embodiment, a spinal implant isprovided having an expandable container with an interior volume that isselectively expandable between a compressed condition and an expandedcondition. The expandable container is coupled to a superior endplatemember having a bone-contacting surface and an engagement surfaceeffective to mate with a superior surface of the expandable containerand an inferior endplate member having a bone-contacting surface and anengagement surface effective to mate with an inferior surface of theexpandable container. In addition, at least one inlet port is formed inthe expandable container and is effective to communicate a fluid to atleast one cavity disposed within the interior volume of the expandablecontainer.

While the implant can have a variety of configurations, in one exemplaryembodiment, the implant can include an angular adjustment mechanismconfigured to enable continuously variable angular adjustment of thesuperior and inferior endplate members with respect to a plane extendinghorizontally therethrough. For example, the angular adjustment mechanismcan include an articulating pleated member, such as a bellows, whichextends between the superior and inferior endplate members.Alternatively, the angular adjustment mechanism can include anarticulating joint, such as a ball joint, disposed within one of thesuperior and inferior endplate members.

In another aspect of the invention, the implant can include acontinuously variable height adjustment mechanism, such as a hydraulicmover. In an exemplary embodiment, the hydraulic mover can be a curablematerial, an expandable balloon, and/or a piston.

While the implant can have many different sizes, in one exemplaryembodiment, the expandable container and the superior and inferiorendplate members have a combined minimum height of about 5 mm in thecompressed condition and a combined maximum height of about 15 mm in theexpanded condition.

In a further aspect of the invention, the superior and inferior endplatemembers are rigid and can include a biocompatible elastomeric component.In an exemplary embodiment, the elastomeric component can be curablepolymers, semi-rigid hydrogels, high-durometer silicones orpolyurethanes.

The invention also relates to methods for distracting two adjacentvertebrae. In one embodiment, the method can include surgicallydelivering a selectively expandable spinal fusion implant into anintervertebral disc space. The implant can then be expanded until asuperior endplate and an inferior endplate of the spinal implant contactopposing bony surfaces of the two adjacent vertebrae and adjustments canbe made to the expansion of the implant until the two adjacent vertebraeare at a desired separation.

The methods disclosed herein are particularly well suited for aminimally invasive surgical procedure in which the spinal fusion implantis delivered through an access port or a cannula. In one exemplarymethod, the minimally invasive surgical procedure is conducted while theimplant is at a compressed height of about 5 mm. Once positioned betweenthe vertebra, the implant can be selectively expanded to any heightappropriate for the intervertebral disc space. Additionally, angularadjustments can be made to the superior and inferior endplates withrespect to a plane extending horizontally therethrough to better conformto a natural lordotic angle of the intervertebral disc space.

These and other aspects of the presently disclosed embodiments will bedescribed in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1A is a perspective view of a self-distracting spinal implant in acompressed condition;

FIG. 1B is a perspective view of the implant of FIG. 1A in an expandedcondition;

FIG. 2A is a perspective view of a free-standing pleated member for usewith a self-distracting spinal implant;

FIG. 2B is a front view of the pleated member of FIG. 2A in thecompressed condition, showing an inlet port;

FIG. 2C is a front view of the pleated member of FIG. 2A, in theexpanded condition;

FIG. 2D is a top sectional view of the pleated member of FIG. 2A,showing an interior volume;

FIG. 3A is a perspective view of a hard-walled, self-distracting spinalimplant in a piston configuration, in the compressed condition;

FIG. 3B is a perspective view of the implant of FIG. 3A in the expandedcondition;

FIG. 3C is a perspective view of the implant of FIG. 3A, showing ahydraulic tool attached;

FIG. 3D is a perspective view of an implant of the type shown in FIG. 3Ain an alternate, round shape showing a hydraulic tool attached;

FIG. 4A is a perspective view of a self-distracting spinal implant in apiston configuration with a pleated member.

FIG. 4B is a top view of the implant of FIG. 4A;

FIG. 5A is a front view of a self-distracting spinal implant in a pistonconfiguration with articulating joints;

FIG. 5B is a front view of the implant of FIG. 5A showing one end plateoriented at an angle;

FIG. 6A is a representation of a self-distracting spinal implant beforeit is compressed for insertion into an intervertebral disc space;

FIG. 6B is a representation of the implant of FIG. 6A in the compressedcondition for insertion in the intervertebral disc space;

FIG. 6C is a representation of the implant of FIG. 6A in the expandedcondition after it is inserted into the intervertebral disc space;

FIG. 7A is a representation of a system for inserting a self-distractingspinal implant into an intervertebral disc space; and

FIG. 7B is a representation of the system of FIG. 7A.

DETAILED DESCRIPTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those skilled in the art will understand that the devices andmethods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present invention.

In general, the presently disclosed embodiments relate to methods forsimultaneously distracting two adjacent vertebral bodies and to spinalimplants configured for self-distraction of the intervertebral discspace. In particular, the self-distracting spinal implants disclosedherein are incrementally adjustable for height and for lordotic angle.In one embodiment, the implant is of an optimal shape for placementwithin the intervertebral disc space and is configured to replicate andrestore a natural angle between two adjacent vertebrae. In anotherembodiment, the implant is configured to contain a bone packing materialto encourage bony ingrowth between two adjacent vertebrae.

In one exemplary embodiment, a spinal implant is provided having anexpandable container with an interior volume that is selectivelyexpandable between a compressed condition and an expanded condition. Theexpandable container is disposed between a superior endplate memberhaving a bone-contacting surface and an engagement surface effective tomate with a superior surface of the expandable container and an inferiorendplate member having a bone-contacting surface and an engagementsurface effective to mate with an inferior surface of the expandablecontainer. In some embodiments, the engagement surface of the superiorendplate and the engagement surface of the inferior endplate can beplanar engagement surfaces. In addition, at least one inlet port isformed in the expandable container and is effective to communicate afluid to at least one cavity disposed within the interior volume of theexpandable container.

FIGS. 1A and 1B illustrate one embodiment of a self-distracting implant10 having a pleated member 12, such as an articulating bellows, disposedbetween a superior endplate member 14 a and an inferior endplate member14 b. The implant 10 can have a variety of shapes and sizes, but in oneembodiment, the implant 10 can be elliptically shaped and it has adistraction envelope in the range of about 5 mm to 15 mm. FIG. 1A showsthe implant 10 in a compressed condition, in which a height H1 is at aminimum of the compression envelope, e.g., about 5 mm. FIG. 1B shows theimplant 10 in an expanded condition, in which a height H2 is at amaximum envelope, e.g., about 15 mm.

In the embodiment illustrated in FIGS. 1A and 1B, the superior endplatemember 14 a includes a superior bone-contacting surface 16 a and aninferior engagement surface 18 a that is configured to mate with asuperior surface of the pleated member 12. The inferior endplate member14 b likewise includes an inferior bone-contacting surface 16 b and asuperior engagement surface 18 b that is configured to mate with aninferior surface of the pleated member 12. The endplate members 14 a, 14b are substantially rigid and can be formed from a variety of knownbiocompatible materials, including carbon fiber reinforced polymer(CFRP), metal, and any metal alloys. In one exemplary embodiment, thesuperior and inferior bone-contacting surfaces 16 a, 16 b are configuredto seat and retain a formable component (not shown) that can conform tothe natural contours of the adjacent vertebra to enhance the fit withinthe intervertebral disc space. A person skilled in the art will realizethat any appropriate biocompatible formable component known in the artcan be used to improve the conformance of the superior and inferiorendplate members 14 a, 14 b. Suitable examples include high-durometersilicones and polyurethanes, in-situ curing resins such aspolymethylmethacrylate (PMMA) (e.g., SmartSet GMV™ by DePuy Orthopedicsof Warsaw, Ind.) and tetraethyleneglycol dimethacrylate (TEGDMA) (e.g.,NRC™ by Dentsply of York, Pa.), curing/setting calcium phosphate cements(e.g., NanOss™ Bone Void Filler by Angstrom Medica of Woburn, Mass.),polyanhydrides, polyvinyl acetates, and polysaccharides (e.g., Eureka™DUET by SurModics of Eden Prairie, Minn.).

As shown in FIG. 1A, when the implant 10 is in the compressed condition,the superior and inferior endplate members 14 a, 14 b can be parallel toone another and to a horizontal plane 26 extending through the implant.Because the endplate members 14 a, 14 b are attached to the pleatedmember 12, however, their angle with respect to each other and withrespect to the horizontal plane 26 can be adjusted. As the implant 10 isexpanded, the endplate members 14 a, 14 b are free to rotate withrespect to the horizontal plane 26 as necessary to compensate for anyheight differences in the implant 10 and any necessary lordotic anglewithin the intervertebral disc space. The pleated member 12 coupled withthe endplate members 14 a, 14 b can allow for a lordotic angle ofanywhere between zero and at least sixteen degrees with respect to thehorizontal plane 26 extending therethrough. This allows the endplatemembers 14 a, 14 b to better conform to any necessary or naturallordotic angle between two adjacent vertebrae.

FIGS. 2A-2D illustrate one example of a pleated member 12 that can beused to form the implant 10 of the type described above. In oneembodiment, the pleated member 12 is expandable and compressible asneeded, having relatively thin walls with a flexible bellows-likestructure. The pleated member 12 can be formed from any suitablematerial known in the art. Some examples of suitable materials includeelastomeric materials, polymeric materials, metals, and metal alloys.

As shown most clearly in FIG. 2D, an interior volume 23 can be disposedwithin the pleated member 12 and is configured for receiving acompressible and curable expansion material which enables the pleatedmember 12 to be expanded as needed. In the alternative, an inner annularopening 20 of the pleated member 12 can contain an expandable balloon(not shown), also configured for receiving an expansion material. Anysuitable compressible and curable expansion material known in the artcan be used to fill the interior volume 23 or the expandable balloon.Some examples of suitable materials include polymethyl methacrylate(PMMA), synthetic cortical bone fillers such as setting/curing calciumphosphate cement (e.g., Cortoss™), tetraethyleneglycol dimethacrylate(Bis-Teg DMA), polyurethane, cyanoacrylate, etc. A person skilled in theart will appreciate that any biocompatible, expandable balloon known inthe art can be used within the inner annular opening 20 of the pleatedmember 12.

In another exemplary embodiment, the interior volume 23 within thepleated member 12 can contain more than one cavity or chamber suitablefor an expansion material, or alternatively, for multiple expandableballoons. Having more than one chamber within the interior volume 23will allow for greater flexibility in height and angle customization.For example, one chamber can be filled to a greater extent than anotherchamber, thereby causing one part of the pleated member 12 to expand toa height greater than another part of the pleated member 12. Inaddition, one chamber can contain an expandable balloon which isexpanded to a greater extent than an expandable balloon within a secondchamber. This would allow the implant 10 to be appropriately configuredfor a more natural lordotic angle within the intervertebral disc space.A person skilled in the art will appreciate that any number of chambersand/or expandable balloons can be used with the pleated member 12 sothat the height and angle of the implant 10 is completely customizable.

FIGS. 2B-2D also illustrate an inlet port 22 formed in the pleatedmember 12 which is effective to communicate a fluid to the interiorvolume 23 of the pleated member 12. In the case where a curableexpansion material is used to expand the implant 10, a filler device canbe attached to and detached from the inlet port 22 via a snap offconnector, a natural hinge, a luer connector, a notch sensitive device,or any other connection mechanism known in the art. In the case where anexpandable balloon is used with the pleated member 12, the mouth orinlet of the balloon can be congruent with the inlet port 22 so that afiller device attached to the inlet port 22 is effective to fill theexpandable balloon. Alternatively, the filler device can enter throughthe inlet port 22 and attach directly to the balloon within the interiorvolume 23 of the implant for filling purposes. A person skilled in theart will appreciate that any filler device known in the art can be usedto fill the interior volume 23 and/or expandable balloon with a curableexpansion material. Although inlet port 22 is shown to be disposedwithin a side of the pleated member 12, one skilled in the art willappreciate that it can alternatively be disposed within the superior orinferior endplate members 14 a, 14 b.

In an exemplary embodiment in which multiple connected chambers are usedwithin the interior volume of the pleated member 12, a person skilled inthe art will appreciate that flow restrictors can be used between thechambers to allow different quantities of material to be injected intodifferent areas of the implant. Additionally or alternatively, the flowrate restrictors can allow material to be injected at different flowrates. Such a design facilitates customization of height and lordoticangle. Alternatively, multiple inlet ports disposed within the sides ofthe pleated member 12 and/or the endplate members 14 a, 14 b can be usedto fill independent multiple chambers or multiple expandable balloons.

The self-distracting spinal implants disclosed herein can be in avariety of shapes, and FIGS. 3A and 3B show one exemplary embodiment ofan elliptical or cashew-shaped, hard-walled implant 100 having a fixedplaten member 102 and a movable platen member 104 in a piston-likeconfiguration. At least a portion of the movable platen member 104 isdisposed within the fixed platen member 102 and the two are slidinglyengaged with one another in a fluid tight seal. A superior endplatemember 106 a includes a superior bone-contacting surface 108 a and aninferior engagement surface 110 a that is configured to mate with asuperior surface of the movable platen member 104. An inferior endplatemember 106 b includes an inferior bone-contacting surface 108 b and asuperior engagement surface 110 b that is configured to mate with aninferior surface of the fixed platen member 102. As shown an innerannular opening 120 may extend through the device. FIG. 3C shows theimplant 100 in a compressed condition, with an inlet port 112 disposedin a side of the fixed platen member 102. The inlet port 112 is in fluidcommunication with an interior volume 123′ (FIG. 3D) that is configuredfor receiving a hydraulic fluid, which can be delivered through anysuitable filler device, such as a hydraulic feed 114.

FIG. 3D shows a similarly constructed implant 100′ in a piston-likeconfiguration, as described above, having a circular configuration. Aninlet port 112′ located in the fixed platen member 102′ is provided, andis configured to receive a hydraulic feed 114′. The inlet port 112′ isin fluid communication with an interior volume 123′ and is configured toreceive a hydraulic fluid, which can be a curable material. FIG. 3D alsoillustrates that the superior and inferior bone-contacting surfaces 116a, 116 b of the implant 100′ include a roughened surface. The roughenedsurface allows the implant 100′ to have a more stable fit within theintervertebral disc space by providing increased friction between thevertebral endplates and the implant 100′. A person skilled in the artwill appreciate that any of the implant embodiments disclosed herein caninclude bone-contacting surfaces formed from any roughened surface knownin the art. A person skilled in the art will also appreciate that any ofthe embodiments disclosed herein can be formed of any geometrical shape.

As shown in FIGS. 3C and 3D, the hydraulic feed 114, 114′, or a similardevice, is configured to communicate a fluid to the interior volume 123′of the piston and thereby cause the movable platen member 104, 104′ tomove relative to the fixed platen member 102, 102′ to expand andincrease the height of the implant 100, 100′. A person skilled in theart will appreciate that an inlet port capable of receiving a hydraulicfeed can also be formed in either of the superior and inferior endplatemembers.

FIGS. 4A and 4B show a further embodiment of a self-distracting spinalimplant 200 having an elliptical or cashew-shape and including a fixedplaten member 202 and a movable platen member 204. At least a portion ofthe movable platen member 204 is disposed within the fixed platen member202 in a piston-like configuration with a fluid tight seal therebetween.A pleated member 206 is contained in a bore 214 formed within themovable platen member 204 such that it extends between a superiorendplate member 208 a and an inferior endplate member 208 b. The pleatedmember 206 is configured to receive a hydraulic fluid (e.g., a curablematerial) for moving the piston. The pleated member 206 provides moreflexibility in the tolerance required for this fluid tight seal than ifthe fixed platen member 202 were mated directly to the movable platenmember 204 without the pleated member 206. As shown in FIG. 4A, thesuperior and inferior endplate members 208 a, 208 b are otherwisecoupled to the movable platen member 204 and the fixed platen member202, respectively, by biocompatible screws 212. The screws 212 can beinserted into the superior and inferior endplate members 208 a, 208 bthrough a superior bone-contacting surface 222 a and an inferiorbone-contacting surface 222 b. A person skilled in the art willappreciate that any appropriate method of attaching the superior andinferior endplate members 208 a, 208 b to the movable platen member 204and the fixed platen member 202 can be used.

In the illustrated embodiment, an inlet port 216 is disposed in thefixed platen member 202 of the implant 200 and is in fluid communicationwith an interior volume 223 of the piston, which is configured forreceiving hydraulic fluid. Fluid is injected into the implant 200 viathe inlet port 216 and a hydraulic feed 218 to cause the movable platenmember 204 and the pleated member 206 to move relative to the fixedplaten member 202 to expand and increase the height of the implant 200.FIG. 4A shows the implant 200 in an expanded condition.

FIGS. 5A and 5B show another exemplary embodiment of a self-distractingspinal implant 300 having two piston members and two articulatingjoints. A first piston member includes a fixed platen member 302 and asuperior movable platen member 304 a disposed within a superior portionof the fixed platen member 302 in a piston-like configuration with afluid tight seal. A second piston member likewise includes the fixedplaten member 302, as well as an inferior movable platen member 304 bdisposed within an inferior portion of the fixed platen member 302 in apiston-like configuration with a fluid tight seal.

In the illustrated embodiment, the superior movable platen member 304 ais connected to a superior endplate member 306 a via an articulatingjoint 308, such as a ball joint, that enables angulation of the superiorendplate member 306 a. The inferior movable platen member 304 b islikewise connected to an inferior endplate member 306 b via anarticulating member 308. In an expanded condition, the superior and/orinferior endplate members 306 a, 306 b can rotate via the articulatingjoint 308 relative to a horizontal plane 312 extending therethrough, asillustrated in FIG. 5B. This allows the implant 300 to conform to anynecessary and/or natural lordotic angle within the intervertebral discspace. A person skilled in the art will appreciate that an inlet portcan be formed in the fixed platen member 302 of the implant 300, as wellas in any other portion of the implant 300. The inlet port can beconfigured to receive a hydraulic feed capable of communicatinghydraulic fluid to an interior volume 310 of the implant. The hydraulicfluid is effective to move the superior and inferior movable platenmembers 304 a, 304 b relative to the fixed platen member 302, therebyexpanding and retracting the implant 300 as necessary.

In use, a variety of surgical techniques, including conventional opensurgery and minimally invasive surgery, can be used to place anexemplary self-distracting implant within the intervertebral disc space.Referring to FIGS. 6A-6C, in one exemplary method, the implant 500 canbe inserted into the intervertebral disc space 502 via an access port orcannula that extends through a patient's skin to a site where theimplant is to be implanted. As shown in FIG. 6B, the implant 500 willinitially be in a compressed condition with a minimal height, forexample, of about 5 mm. After placement within the disc space 502, theimplant 500 can be expanded to distract two adjacent vertebrae 504, 506by an appropriate amount up to the implant's maximum height, forexample, of about 15 mm. After distraction, any necessary angularadjustments can be made so that the implant 500 conforms to the naturallordotic angle and spacing between the adjacent vertebrae 504, 506, asshown in FIG. 6C.

In another exemplary method involving the implant 10 illustrated inFIGS. 1A and 1B, the implant 10 can be inserted through a cannula orport and into a disc space in a compressed condition with a minimumheight of about 5 mm. A compressible and curable expansion material suchas PMMA, synthetic cortical bone fillers, such as calcium phosphatecement (e.g., Cortoss™), tetraethyleneglycol dimethacrylate (Bis-TegDMA), polyurethane, cyanoacrylate, polysaccharides, polyanhydride, insitu curing silicone, etc., is then injected into the interior volume,multiple chambers, or expandable balloon of the pleated member 12 by afiller device. As the material is injected, the superior and inferiorendplate members 14 a, 14 b move apart upon expansion of the pleatedmember 12 so that they contact and apply a distraction force to the twoadjacent vertebrae, causing them to distract. The filler material isinjected into the interior volume until the vertebrae are at a desiredseparation. The pleated member 12 allows the implant 10 to conform to anatural lordotic angle as it expands. After the necessary height andangle are achieved, the material can be quickly cured by light orchemical so that the material forms a solid plug within the implant 10,thereby retaining the customized height and lordotic angle. A personskilled in the art will appreciate that any biocompatible, compressible,and curable material known in the art can be injected into the implant10 to distract the vertebrae. A person skilled in the art will alsoappreciate that the implant 10 can be expanded to any height within itsdistraction envelope of between about 5 mm and 15 mm.

In another exemplary method involving use of the implants illustrated inFIGS. 3A-3D and in FIGS. 4A-4B, the implant 100, 200 is inserted into adisc space in a compressed condition with a minimum height of about 5mm. A hydraulic fluid (which can be curable) is then injected into theinterior volume 123′, 223 of the piston via the hydraulic feed. Themovable platen member 104, 204 moves relative to the fixed platen member102, 202 to cause the implant 100, 200 to expand. The superior andinferior bone-contacting surfaces exert a pressure on the adjacentvertebrae, causing them to distract. The surgeon can thereby adjust thespacing between the adjacent vertebrae by adjusting the height of theimplant 100, 200 up to its maximum height of about 15 mm. When thedesired spacing between the vertebrae has been achieved, the hydraulicfeed can be removed (and cured in the case of a curable material), andthe implant 100, 200 will remain at the desired height, providingsupport and stabilization between the vertebrae.

In a further exemplary method involving the use of the implant 300illustrated in FIGS. 5A and 5B, the implant 300 is inserted within adisc space in a compressed condition with a minimum height of about 5mm. A hydraulic fluid (which can be curable) is then injected into theinterior volume 310 of the piston via the hydraulic feed. The superiorand inferior movable platen members 304 a, 304 b move relative to thefixed platen member 302 to cause the implant 300 to expand. The superiorand inferior bone-contacting surfaces thus exert a pressure on theadjacent vertebrae, causing them to distract as the implant 300 isexpanded. The surgeon can thereby adjust the spacing between theadjacent vertebrae by adjusting the height of the implant 300 up to itsmaximum height of about 15 mm. In addition, the surgeon can make angularadjustments to the superior and/or inferior endplate members 306 a, 306b via the articulating joints 308 relative to the horizontal plane 312so that the implant 300 better conforms to the necessary and/or naturallordotic angle between the adjacent vertebra. When the desired spacingand angle between the vertebrae has been achieved, the hydraulic feedcan be removed (and cured in the case of a curable material), and theimplant 300 will remain at the desired height and angle, providingsupport and stabilization between the vertebrae.

In still another exemplary method, a person skilled in the art willappreciate that multiple pistons can be used in combination withmultiple pleated members within one implant to obtain heightcustomization as well as angle customization within the intervertebraldisc space. After the implant is inserted in a compressed condition,each piston member can be independently adjusted to achieve differentheights, which allows the implant to conform to any necessary or naturallordotic angle of the disc space. The pleated members are configured forreceiving a hydraulic fluid and provide flexibility in the tolerancerequired for the fluid tight seal that exists between a movable platenmember of each of the multiple pistons and a superior endplate member. Ahydraulic feed can be used to activate the pistons and can be removedonce the required height and angle of the implant has been achieved.

Referring now to FIGS. 7A and 7B, another exemplary method for insertinga self-distracting spinal implant will be discussed. In the illustratedembodiment, a system is pre-assembled to include a self-distractingspinal implant 600 attached to an insertion tool, such as a cannula 602.As shown, a liquid feed device 604 is in fluid communication with thecannula 602 to inject a curable expansion material into the implant 600.A fluid control valve 606 is disposed on a proximal end of the liquidfeed device 604 so that the flow of the curable expansion material canbe controlled. In addition, a fiber optic cable 608 is disposed withinthe cannula 602 and its distal end extends into an inlet port of theimplant 600 to facilitate curing of the injected material. The fiberoptic cable 608 can be attached at its proximal end to any suitablesource of curing energy, such as a high intensity light-emitting diode(LED) disposed within a housing 610 as shown in FIG. 7B.

In use, the implant 600 is attached to a distal end of the cannula 602and is initially in a compressed condition with a height, for example,of about 5 mm. Using the cannula 602, the implant 600 is insertedthrough a minimally invasive surgery access port 612 that extendsthrough a patient's skin to a site where the implant is to be implanted,and which can be located adjacent to the relevant vertebral bodies 614,614′. The implant 600 is maneuvered into the intervertebral disc spacewith the cannula 602. Once in place, the fluid control valve 606 isopened to allow a curable expansion material to flow through the cannula602 and into the interior volume of the implant 600. As the fluid isinjected, the implant 600 expands and causes the distraction of theadjacent vertebrae 614, 614′ to any height up to the implant's maximumheight of about 15 mm. By maneuvering the implant 600 and adjusting thefluid flow of the curable material, a surgeon can then make anynecessary adjustments to the distraction space and the relative force ofthe implant 600 on the vertebrae 614, 614′. In addition, angularadjustments can be made to the implant 600 to compensate for anyrequired lordotic angle between the vertebrae 614, 614′. Once theseadjustments have been made, the curing energy can be activated toessentially instantaneously cure the material within the implant 600,forming a solid plug that will retain the height and angularrequirements of the disc space. The cannula 602 can then be removed fromthe implant 600, for example, by breaking or snapping a notchattachment. A person skilled in the art will appreciate that the cannula602 can be joined to and detached from the implant 600 by any methodknown in the art. A person skilled in the art will also appreciate thatthe implant 600 can be expanded to and kept at any height within itsdistraction envelope of between about 5 mm and 15 mm.

The self-distracting spinal implants disclosed herein are particularlywell suited for minimally invasive surgery. That is, theself-distracting implants disclosed herein have a compressed envelopewith a height of about 5 mm and can easily be inserted via a minimallyinvasive surgery port, without the need of an open surgical procedure.Such procedures, which are generally well known to those skilled in theart, tend to result in less operative trauma for the patient than moreinvasive procedures. Minimally invasive procedures also tend to be lessexpensive, reduce hospitalization time, cause less pain and scarring,speed recovery, and reduce the incidence of post-surgical complications,such as adhesions.

In addition to the various features discussed above, theself-distracting spinal implants described herein can be adapted so asto allow for spinal fusion and/or spinal fixation. Any of the implantdesigns disclosed herein can include or be formed of a fusion-promotingbioactive material so that the implant actively participates in spinalfusion. In an exemplary embodiment, the implant is made from a bioactivematerial. In another embodiment, a bioactive material can be formed as acoating on a non-bioactive material from which the implant is formed. Instill a further embodiment, the implant can be filled with a bioactivematerial so that bony ingrowth through the implant and between thevertebra is allowed and encouraged. For example, the implant can beformed of a metal or CFRP and be coated or filled with afusion-promoting bioactive material. Exemplary fusion promotingbioactive materials can include allograft bone, tricalcium phosphates(TCP), hydroxyapatite, Biocryl Rapide™ (tricalcium phosphate loadedpoly-L-lactic acid/Poly-glycolic acid), bioglass, plasma sprayedtitanium, hydroxyapatite-coated titanium, surface textured titanium, andpolymer composites.

One skilled in the art will appreciate further features and advantagesof the invention based on the above-described embodiments. Accordingly,the invention is not to be limited by what has been particularly shownand described, except as indicated by the appended claims. Allpublications and references cited herein are expressly incorporatedherein by reference in their entirety.

What is claimed is:
 1. A surgical method, comprising: inserting an implant into an intervertebral space between two adjacent vertebrae, the implant having a superior endplate, an inferior endplate, and an expandable articulating pleated member that extends between the superior and inferior endplates and is expandable between a compressed condition and an expanded condition, the expandable articulating pleated member having a sidewall with an inward-facing surface, an outward-facing surface, an interior volume disposed within the sidewall between the inward-facing surface and outward-facing surface, and an inner annular opening that extends from a superior-facing surface of the pleated member to an inferior-facing surface of the pleated member; and delivering fluid into a balloon placed within the inner annular opening of the articulating pleated member to expand the articulating pleated member to the expanded condition, wherein the implant is inserted into the intervertebral space with the pleated member in the compressed condition.
 2. The method of claim 1, wherein expanding the articulating pleated member increases a separation between the superior endplate and the inferior endplate.
 3. The method of claim 2, wherein increasing the separation between the superior endplate and the inferior endplate applies a distraction force to the two adjacent vertebrae.
 4. The method of claim 1, further comprising delivering the fluid into the balloon until a desired separation extends between the two adjacent vertebrae.
 5. The method of claim 1, wherein delivering the fluid into the balloon conforms the implant to a natural lordotic angle of a patient's spine as the implant expands.
 6. The method of claim 1, wherein delivering the fluid into the balloon further comprises delivering the fluid through an inlet port of the pleated member, the inlet port extending from the outward-facing surface of the pleated member to the inward-facing surface of the pleated member.
 7. The method of claim 1, wherein delivering the fluid into the balloon rotates at least one of the superior endplate and the inferior endplate with respect to a horizontal plane as the fluid is delivered into the balloon.
 8. The method of claim 1, wherein delivering the fluid into the balloon independently adjusts an angle of the superior endplate and the inferior endplate relative to a horizontal plane as the pleated member expands.
 9. The method of claim 1, wherein the superior endplate and the inferior endplate of the implant extend parallel to one another when the articulating pleated member is in the compressed condition.
 10. The method of claim 9, wherein delivering the fluid into the balloon expands the pleated member such that the superior endplate and the inferior endplate extend with a non-parallel relationship to one another.
 11. The method of claim 1, wherein the expandable articulating pleated member and the superior and inferior endplates have a combined minimum height of about 5 mm when the articulating pleated member is in the compressed condition and a combined maximum height of about 15 mm when the articulating pleated member is in the expanded condition.
 12. The method of claim 1, wherein the fluid is a curable expansion material.
 13. The method of claim 12, further comprising curing the fluid with a light or a chemical such that the fluid forms a solid within the balloon.
 14. A spinal implant, comprising: a superior endplate having a superior bone contacting surface and an inferior engagement surface; an inferior endplate having an inferior bone contacting surface and a superior engagement surface; an expandable articulating pleated member that extends between the superior and inferior endplates and is mated to the engagement surfaces of the superior and inferior endplates, the expandable articulating pleated member being selectively expandable between a compressed condition and an expanded condition, the expandable articulating pleated member having a sidewall with an inward-facing surface, an outward-facing surface, and an interior volume disposed within the sidewall between the inward-facing and outward-facing surfaces, the interior volume having at least one chamber for holding a fluid, and the sidewall forming an inner annular opening of the pleated member; an expandable balloon configured to receive an expansion material and placed within the inner annular opening of the expandable articulating pleated member; and an inlet port effective to communicate the expansion material into the expandable balloon; wherein delivery of the expansion material through the inlet port and into the expandable balloon increases a distance between the superior and inferior endplates and thereby increases a height of the expandable articulating pleated member; and wherein the inlet port extends through the outward-facing surface and the inward-facing surface of the articulating pleated member.
 15. The implant of claim 14, wherein the fluid is a curable material.
 16. The implant of claim 14, wherein the superior and inferior endplates are rigid.
 17. The implant of claim 14, wherein the expandable articulating pleated member and the superior and inferior endplates have a combined minimum height of about 5 mm in the compressed condition and a combined maximum height of about 15 mm in the expanded condition.
 18. The implant of claim 14, wherein the inferior engagement surface of the superior endplate is planar and an outer periphery of the planar inferior engagement surface is exposed when the expandable articulating pleated member is in the expanded condition; and wherein the superior engagement surface of the inferior endplate is planar and an outer periphery of the planar superior engagement surface is exposed when the expandable articulating pleated member is in the expanded condition.
 19. The implant of claim 14, wherein the expandable articulating pleated member has a superior surface and an inferior surface, the superior surface and inferior surface extending between the inward-facing surface and outward-facing surface such that the interior volume is defined by the superior surface, the inferior surface, the inward-facing surface, and the outward-facing surface.
 20. The implant of claim 14, wherein the sidewall of the expandable articulating pleated member is a single continuous sidewall. 